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Basics ⬇

Basics

Definition

Inflammation of the cornea associated with loss of the corneal epithelium (corneal erosion) or loss of variable amounts of the underlying corneal stroma (corneal ulcer).

Pathophysiology

  • May be caused by any condition (traumatic or non-traumatic) that disrupts the corneal epithelium or stroma.
  • Ulcers-classified as superficial or deep, uncomplicated or complicated.
  • Superficial-involves the epithelium and possibly the superficial stroma.
  • Deep-involves a greater thickness of stroma and may extend to Descemet's membrane (descemetocele), possibly leading to rupture of the globe.
  • Complicated-persistence of underlying/inciting cause, microbial infection, or production of degradative enzymes.
  • Epithelial wound healing-adjacent corneal epithelial cells loosen and begin migration over the defect within a few hours; mitosis occurs within a few days to restore normal epithelial thickness; healing process complete in 5–7 days in uncomplicated, superficial ulcers.
  • Stromal wound healing-slower, more complex; can be in an avascular or vascular manner; in shallow wounds, epithelial migration may be sufficient to fill the defect; epithelium may cover some deeper ulcers even when epithelium and stromal regeneration are insufficient to restore normal corneal thickness (non-ulcerated divot defect is called a facet); stroma usually heals by fibrovascular infiltration, which may take several weeks and often results in loss of or decrease in corneal clarity.
  • Stromal ulcers-often complicated by microbial infection or enzymatic destruction initiated by microbial organisms, host inflammatory cells, or corneal epithelial or stromal cells; enzymatic destruction may result in gelatinous appearance of the corneal stroma, called a melting or malacic ulcer.

Systems Affected

Ophthalmic

Genetics

  • No proven basis, although breed predilections are seen.
  • May be secondary to other corneal diseases that have breed predispositions and presumably a genetic basis, such as corneal epithelial dystrophy in Shetland sheepdogs and corneal endothelial dystrophy in Boston terriers.

Incidence/Prevalence

Common

Signalment

Species

Dog and cat

Breed Predilections

  • Dogs-brachycephalic breeds predisposed.
  • SCCED/indolent erosion-occurs in any breed.
  • Cats-Persian, Himalayans, Siamese, and Burmese predisposed to feline corneal sequestrums (see Corneal Sequestration-Cats).

Mean Age and Range

  • Age of onset-variable; determined by cause.
  • SCCED-middle-aged and older dogs.

Signs

Historical Findings

  • May be acute or chronic (SCCED).
  • Tearing, squinting, rubbing at eyes.
  • Owners may report the appearance of a film over the eye (often corneal edema); prolapsed third eyelid.
  • Herpetic ulcers (cats)-may have history of respiratory disease.

Physical Examination Findings

  • Nonspecific-serous to mucopurulent ocular discharge, blepharospasm, nictitans prolapse, conjunctival hyperemia.
  • Superficial-may note one or more circumscribed, linear, or geographic defects in the cornea.
  • Deep stromal ulcer or descemetocele-may appear as a crater-like defect.
  • Depending on cause and duration-may see neovascularization, pigmentation, scarring, inflammatory cell infiltrate (yellow to cream-colored opacity with indistinct margins, often surrounded by corneal edema), collagenolytic activity (melting) of the corneal stroma.
  • SCCED-loose or redundant epithelial edges; may demonstrate fluorescein stain extending into areas with seemingly intact epithelium (ring of less intense staining).
  • Reflex anterior uveitis-mild or severe, secondary to ulceration; severe may result in hypopyon; severe suggests concurrent bacterial infection.

Causes

  • Trauma-blunt; penetrating; perforating.
  • Adnexal disease-ectopic cilia, entropion, ectropion, eyelid mass, distichiasis.
  • Lagophthalmos (inability to close eyelids completely)-results in exposure keratitis; may be breed related in brachycephalic dogs and cats; may be caused by exophthalmos, buphthalmos, or may be neuroparalytic from facial nerve paralysis.
  • Tear-film abnormality-quantitative tear deficiency (KCS); qualitative tear film deficiency caused by mucin deficiency or some other unidentified tear abnormality.
  • Infection-usually secondary in dogs; can be primary infection of herpesvirus in cats.
  • Primary corneal disease-endothelial dystrophy; other endothelial disease.
  • Miscellaneous-foreign body (corneal or conjunctival); chemical burns; neurotrophic keratitis (loss of trigeminal sensation); immune-mediated disease.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Fluorescein dye retention-diagnostic.
  • Other causes of a red and painful eye-conjunctivitis, uveitis, KCS, glaucoma (see Red Eye).
  • May develop concurrently with other causes of a red eye (e.g., secondary to KCS).

Other Laboratory Tests

  • Corneal culture and sensitivity-aerobic bacteria; particularly for complicated, deep, or rapidly progressive corneal ulcers.
  • Herpesvirus (cats)-PCR or IFA for herpesvirus available; negative test does not rule out herpesvirus infection.

Diagnostic Procedures

Fluorescein Staining

  • Homogeneous stain uptake-superficial or stromal ulcer; may be circular to geographic, linear, or combination; location and shape may help determine cause (e.g., linear may indicate foreign body or rubbing of ectopic cilia); interpretation of depth subjective.
  • SCCED-may have leakage of stain under surrounding loose epithelium.
  • Crater-like defect that retains stain at the periphery but is clear at center-Descemetocele-may also see Descemet's membrane bulging forward if defect is large.
  • Crater-like defect with pooling of stain transiently but can be easily rinsed-previous stromal ulcer that has epithelialized (facet); must be distinguished from a descemetocele.

Other

  • Cytologic evaluation of cornea and gram, Giemsa, or Wright staining may reveal microbial or fungal organisms and may help direct initial antimicrobial therapy.
  • Rose bengal corneal stain (cats) may delineate superficial, linear, epithelial ulcers (dendritic ulcers), which are considered pathognomonic for herpesvirus infection.
  • Schirmer tear test may identify ulceration associated with KCS; it is contraindicated in very deep ulcers or descemetoceles.

Pathologic Findings

  • Ulcers-typically suppurative inflammation, possibly neovascularization, loss of epithelium and basement membrane; possibly organisms.
  • SCCEDs-superficial hylanized zone in stroma; epithelial lipping around erosions; varying degrees and types of leukocytic infiltrate and fibrosis.

Treatment ⬆ ⬇

Treatment

Appropriate Health Care

Hospitalize deep or rapidly progressive ulcers; these may require surgery and/or frequent medical treatments.

Nursing Care

Keep facial hair out of eyes and clean.

Activity

  • Restrict with deep stromal ulcer or descemetocele to prevent rupture.
  • Prevent self-trauma with Elizabethan collar.

Client Education

  • Instruct client to wait at least 5 minutes between medications if more than one ophthalmic drop is prescribed; wait longer between ointments.
  • Advise client to contact veterinarian if patient appears more painful or the eye markedly changes in appearance.
  • SCCED-discuss protracted course with client; usually achieve healing within 2–6 weeks but may require weekly rechecks and multiple procedures.

Surgical Considerations

  • Superficial ulcers do not usually require surgery if the inciting cause has been eliminated.
  • Ulcer that extends one-half or greater corneal thickness and particularly to Descemet's membrane may benefit from surgery.
  • Descemetocele or full-thickness corneal laceration-considered a surgical emergency for possible referral.

Procedures

  • SCCED-debridement of loose epithelium with a dry, sterile, cotton-tipped swab after application of topical anesthesia (50% success rate); punctate or grid keratotomy easily performed after epithelial debridement with topical anesthesia (80% success rate); superficial keratectomy is more invasive and may cause more scarring but has 100% success rate; application of a contact lens or nictitans flap after any of these procedures may improve comfort and aid healing.
  • Diamond burr keratotomy for SCCED/indolent erosion only; use gently over surface of erosion; may be associated with increased risk of infection post-procedure.
  • Rotational pedicle conjunctival flap, corneoscleral transposition, corneal transplant-surgical procedures for ulcers >50% thickness of the stroma and descemetoceles.
  • Cyanoacrylate repair (corneal glue)-can be used for deep ulcers; promotes corneal vascularization and stabilizes cornea, but has somewhat lower success rate compared to other corneal surgeries.

Medications ⬆ ⬇

Medications

Drug(s) Of Choice

Antibiotics

  • Topical agents-indicated for all patients.
  • Frequency of application-determined by severity and the preparation used; ointments have a relatively long contact time and are applied q6–12h; solutions are applied more frequently (4, 6, 8, or even 12 times daily) in the initial treatment of complicated ulcers; solutions probably more appropriate in deep ulcers.
  • Commonly used agents-erythromycin (cats); triple antibiotic, gentamicin, and tobramycin.
  • Uncomplicated ulcers or superficial erosions-combination of neomycin, polymyxin B, and bacitracin an excellent first choice; broad spectrum of antimicrobial activity; often used 2–3 times/day for prophylactic therapy.
  • Complicated ulcers-often use combination therapy of cefazolin (use IV solution to make 33–50 mg solution in saline or artificial tears for topical use) with either an aminoglycoside (tobramycin, gentamicin) or fluoroquinolone (ciprofloxacin, ofloxacin); particularly in rapidly progressive, deep, or melting ulcers; frequency depends on severity but usually a minimum of q3–4h.

Atropine

  • 1% ointment or solution.
  • Indicated for reflex anterior uveitis; frequency-usually q8–24h to effect (mydriasis).

Antiviral Agents

  • Indicated for herpetic ulcers in cats.
  • Trifluridine (Viroptic) solution-q4–6h until clinical response is observed; then reduce for 1–2 weeks after clinical signs have subsided.

Nonsteroidal Anti-inflammatory Drugs

  • May be indicated for anti-inflammatory and analgesic properties.
  • Aspirin: dogs, 10–15 mg/kg PO q12h.

Contraindications

  • Topical corticosteroids-contraindicated with any corneal erosion or ulcer.
  • Topical NSAIDs-contraindicated with herpetic ulcers, melting ulcers.
  • Topical atropine-contraindicated with glaucoma, KCS.

Precautions

  • Topical NSAIDs (flurbiprofen, diclofenac)-may delay corneal healing, may potentiate corneal melting.
  • Trifluridine, neomycin-may be irritating.
  • Topical cyclosporine can be used safely in uncomplicated ulcer in KCS patients.

Possible Interactions

Combining antibiotics in solution may inactivate some antibiotics.

Alternative Drug(s)

  • Acetylcysteine-anticollagenolytic agent used for treatment of melting ulcers; efficacy is controversial; dilute 20% stock solution to 5–10% with artificial tears; apply q2–4h.
  • Autologous serum-anticollagenolytic agent; keep refrigerated; avoid contamination; discard after 48 hours.

Follow-Up ⬆ ⬇

Follow-Up

Patient Monitoring

  • Superficial ulcers-repeat fluorescein stain in 3–6 days; if it persists 7 days or longer, either inciting cause has not been eliminated or the patient has an SCCED.
  • Deep stromal or rapidly progressive ulcers-assess every 24 hours initially if outpatient until improvement is seen; many of these patients are hospitalized or undergo surgery; decrease frequency of antibiotic therapy as condition improves.

Prevention/Avoidance

  • Brachycephalic dogs-lubricant ointment administration, permanent partial tarsorrhaphy surgery, or both may help prevent recurrent ulceration.
  • KCS-related ulcers-lifelong treatment of KCS (cyclosporine) or parotid duct transposition surgery to prevent continued ulceration.
  • Herpesvirus (cats)-may try oral lysine 250 mg PO q12h to prevent viral replication; may decrease severity and/or frequency of outbreaks.

Possible Complications

Progressive corneal ulceration-rupture of globe; endophthalmitis; secondary glaucoma; phthisis bulbi; blindness; blind and painful eye (may require enucleation).

Expected Course and Prognosis

  • Uncomplicated superficial ulcer-usually heals in 5–7 days.
  • SCCED-may persist for weeks to months; may require multiple procedures.
  • Deep corneal ulcer treated medically-may require several weeks for fibrovascular repair of defect; does not always granulate satisfactorily; continued deterioration of ulcer and globe rupture are possible.
  • Deep ulcer treated with conjunctival flap-frequently results in more comfort within a few days after surgery; blood supply to flap can be cut in 4–6 weeks if healed well to decrease scarring.

Miscellaneous ⬆

Miscellaneous

Abbreviations

  • IFA = immunofluorescent antibody test
  • KCS = keratoconjunctivitis sicca
  • NSAID = nonsteroidal anti-inflammatory drug
  • PCR = polymerase chain reaction
  • SCCED = spontaneous chronic corneal epithelial defects

Author Ellison Bentley

Consulting Editor Paul E. Miller

Client Education Handout Available Online